The present invention relates to disc drives. More particularly, the present invention relates to crash stops on an actuator arm assembly used in moving a head gimbal assembly across the surface of a disc in a disc drive.
A typical magnetic disc drive includes one or more magnetic discs, a transducer supported by a hydrodynamic air bearing which flies above each magnetic disc, and a drive controller for controlling the disc drive based on commands received from a host system. The drive controller controls the disc drive to retrieve information from the magnetic discs and to store information on the magnetic discs.
An electromechanical actuator operates within a negative feedback, closed-loop servo system. The actuator moves the transducer radially over the disc surface for track seek operations and holds the transducer directly over a track on the disc surface for track following operations.
Information is typically stored on the magnetic discs by providing a write signal to the transducer to encode flux reversals on the surface of the magnetic disc representing the data to be stored. In retrieving data from the disc, the drive controller controls the electromechanical actuator so that the transducer flies above the magnetic disc, sensing the flux reversals on the magnetic disc and generating a read signal based on those flux reversals. The read signal is then decoded by the drive controller to recover the data represented by flux reversals stored on the magnetic disc, and consequently represented in the read signal provided by the transducer.
Conventionally, the electromechanical actuator includes an actuator arm assembly which is coupled to a head gimbal assembly (which includes the transducer and hydrodynamic air bearing). The actuator arm assembly is controlled to pivot about a pivot point to move the head gimbal assembly over the surface of the disc to a desired radial position. The actuator arm assembly typically includes an actuator arm and a voice coil which is connected to the actuator arm. A magnet, or group of magnets, is positioned relative to the voice coil such that when the disc drive controller causes current to flow through the voice coil, the fields generated by the voice coil interact with the magnetic field provided by the magnets to cause movement of the actuator arm assembly about the pivot point.
Such actuator arm assemblies are movable between two extreme positions. In the first extreme position, the actuator arm assembly is positioned to hold the hydrodynamic air bearing over the inner most radius of the magnetic disc. In the second extreme position, the actuator arm assembly is positioned to hold the hydrodynamic air bearing over the outer most radius of the disc.
In order to prevent the actuator arm assembly from moving beyond the first or second extreme positions and off of the surface of the disc, crash stops and stop pins have conventionally been connected inside the housing of the disc drive to physically prevent the actuator arm assembly from moving beyond either the first or second extreme positions. The stop pins are conventionally removable pins which are fastened to a base plate of the housing with screws, or by press fitting. The crash stops are conventionally resilient members which are screwed or press fit into the stop pins. The crash stops extend out and away from the stop pins so that, just before the actuator arm assembly reaches one of the first or second extreme positions, it engages the crash stop. If the actuator arm assembly continues toward the first or second extreme position, it forces the crash stop to deflect toward the stop pin. This deflection continues until the portion of the crash stop which extends away from the stop pin comes into physical contact with the stop pin. At that point, movement of the actuator arm assembly is substantially halted so that the actuator arm assembly cannot move beyond the extreme position.
Because the crash stops and stop pins are conventionally both discrete parts, each must to be assembled into the disc drive. Whether these parts are connected by press fitting or through the use of screws, they are quite labor intensive to assemble. In addition, because these parts are discrete parts, each of the parts must be stocked, and included in the parts count of the disc drive. Thus, the parts undesirably increase the cost of the disc drive and decrease assembly efficiency.